Life

Are You Low on the Sunshine Vitamin?

Top up your vitamin D know-how to stay healthy when the light is low.

by Susan Kitchen

When the days get shorter and the temperatures get cooler, triathletes who live and train in the northern hemisphere flock to indoor pools and indoor trainer sessions. The line for the treadmills at the gym is longer than ever. Despite our best efforts to follow a balanced diet, low vitamin D intake combined with reduced sunlight exposure can be a problem for all athletes. Read on to find out why you should be focusing on this important vitamin.

What is vitamin D?

Vitamin D is one of four fat-soluble vitamins (A, D, E, and K), and requires dietary fat to be absorbed properly. We store fat-soluble vitamins in our body with the exception of vitamin D. Over two-thirds of the US population is at risk of vitamin D deficiency and may not even know it.

What does it do?

For starters, vitamin D is essential for calcium and phosphorus absorption as well as metabolism, and plays a key role in maintaining bone health. Additionally, research strongly suggests that vitamin D is a major component in injury prevention, improved neuromuscular function, increased type II muscle fiber size, and reduced inflammation. It also reduces the risk of stress fractures, strengthens the immune system, and improves overall health. What does this mean for you? Vitamin D can help you get and stay lean, while staving off those annoying bouts of flu and season-ending injuries.

Vitamin D and calcium

Vitamin D regulates calcium absorption, and together they play a vital role in an endurance athlete's diet. Calcium is the most abundant mineral in the body, 98 percent of calcium is found in bone mass, and the remaining two percent circulates in the bloodstream and in our teeth. As endurance athletes, we lose calcium (and sodium) via sweat during strenuous exercise, and unlike vitamin D, we require more dietary calcium than our sedentary counterparts. From this calcium loss and, often, inadequate calcium intake, we are more susceptible to bone loss, osteoporosis (loss of bone mass), and fractures. Additionally, after age 35, our body's natural bone-building process begins to decline, so bone mass becomes even more important. Without adequate vitamin D, we absorb only 10–15 percent of the calcium we consume compared to the standard 30 percent.

Are you at risk?

If you've got a history of stress fractures, bone or joint injuries, muscle pain or weakness, and tend to train indoors a lot, you should have your vitamin D blood levels assessed. Another group that could be at risk are athletes who are dairy-free. Your Vitamin D blood levels should come in at 32-50 ng/ml, which is optimal to offset training stress, resulting in a stronger you. (Blood levels less than 30 ng/ml are considered insufficient.)

Our ability to make vitamin D from sunlight decreases as we age, so older athletes and those with limited sun exposure may be candidates for supplementation and increased vitamin D/calcium-rich food intake. If you live in the northern part of the US and Canada, you may not get enough sun exposure between October and April.

Try this:

Sun exposure without sunscreen: Aim for 10 minutes for lighter skin and 20–30 minutes for darker complexions at least three times per week during the middle of the day. The more skin exposed, the more vitamin D you absorb. If you are effectively making vitamin D from sunlight, you’ll notice that the skin will turn slightly pink from exposure.

Although male athletes are not exempt from decreased bone mass or stress fractures, these issues are more prevalent in female athletes. Common symptoms of low bone-mineral density in females include but are not limited to low energy availability, amenorrhea, abnormal menstrual cycles, and low estrogen levels. Inadequate calcium intake further increases the risk of stress fractures and decreased bone mass.